Much progress has been made in the development of PDP apparatus that serve as flat panel displays in large, wall-mount television and high-definition television displays which are used in place of conventional CRTs. In the direct current (DC) PDP apparatus of FIG. 5, a pair of glass substrates (501 and 502) having a plurality of anodes (503) and cathodes (504) positioned perpendicular, the anodes are covered with an insulator layer (505) as needed on the inner surface of the substrate (502) and the anodes (503) and cathodes (504) are positioned facing each other to maintain a specific gas discharge distance, the cell (508) is then coated with a phosphor material (506) chosen from blue, green and red and the edges thereof are sealed airtight with a sealing material, after which the above-mentioned gas discharge area is filled with a specific discharge gas (509) to create a gas discharge section. A structure is employed whereby the above-mentioned gas discharge distance is kept identical and discharge occurs in a specific cell partitioned by an insulator barrier-rib (507).
PDP apparatus are being made larger and more precise and converted to color. Therefore, a need for a more uniform barrier-rib height, i.e., electrode spacing is required. At the same time, there is a need for cost effective manufacturing of the apparatus.
Screen printing is the most commonly used method for forming the barrier-ribs used in a PDP apparatus. As discussed in published Japanese Patent Application 58-150248, screen printing involves a step in which an insulator powder such as glass is made into a printable paste, after which lines or dots and spaces are paired and printed in layers to a specific thickness at a resolution of about 3 pairs per millimeter, for example, using a screen printing mesh mask (in the case of a small display). At least three or four layers, and at most about fifteen layers, are built up through repeated printing to a specific thickness (height) while the above-mentioned resolution is maintained. This multiple printing step therefore requires an accuracy check of position at each stage of the printing, care must be taken to avoid oozing of the paste at each stage. Furthermore, the film thickness must be precisely controlled so that the final height of the layers is uniform, all of which makes this an extremely complicated step with a low yield. An experienced printing technician has to spend a great deal of time and effort to get around the drawbacks to this step, which incurs tremendous costs.
In light of this situation, a sandblasting barrier-rib formation method has been developed and put into practical use in recent years. The method will be described while referring to FIG. 4. The first step is to form an anode (402) on a glass substrate (401). The insulator layer (406) that serves as the barrier-rib is then screen-printed to the desired thickness. A photoresist (403) that is resistant to sandblasting is bonded over the dried insulator layer and patterned, an abrasive material (404) is sprayed by a sandblasting machine (405). To remove the insulator material from the region in which the resist has not been patterned (407) and the resist is then stripped away and the remaining product fired, which forms a fine barrier-rib of a uniform height.
The above-mentioned screen printing method, in which an insulator layer in the desired pattern is printed to the desired height using a paste whose principal component is an insulator powder such as glass.
Although positioning is easy with a sandblasting method because it involves solid unpatterned printing, the printing still has to be repeated a number of times, and achieving a uniform film thickness is still difficult. Furthermore, because of the need for the barrier-rib of a PDP apparatus to be reliable, this method requires careful paste preparation and printing work so as to avoid any defects in the process, and the work environment and atmosphere also must be carefully managed and improvement in work or production efficiency remains a problem in the industry.
The inventors perfected the present invention upon discovering that a reliable barrier-rib with an uniform height or thickness can be formed easily and the barrier-rib formation step can be greatly improved upon by using a pre-formed green tape of an uniform thickness for the insulator layer.